{"id":"EUVD-2026-38549","revision":null,"records":[{"revision":"ad14a5ec0c024a68825a692d496034c0","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-55517","aliases":[],"title":"Deno: Denial of service via non-ASCII bytes in WebSocket response headers","description":"Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.5, a Deno program that opens a client WebSocket connection could be crashed by the remote server. While handling the WebSocket handshake response, Deno parsed the Sec-WebSocket-Protocol and Sec-WebSocket-Extensions response headers in a way that assumed their bytes were always printable ASCII. A response header containing non-visible-ASCII bytes (0x80-0xFF) caused a panic that aborted the entire Deno process. This vulnerability is fixed in 2.7.5.","state":0,"publishedAt":"2026-06-23T17:24:59.498+00:00","modifiedAt":"2026-06-23T17:52:56.96+00:00","affected":[{"ecosystem":"Vendor product","name":"deno","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"denoland\",\n                    \"product\": \"deno\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 2.7.5\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","score":4.3,"severity":"MEDIUM"}],"references":["https://github.com/denoland/deno/security/advisories/GHSA-x2qc-cmh9-f4hf"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-55517","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-55517","identifiers":["CVE-2026-55517"]},"retained":false,"historicalAffected":[]},{"revision":"f7fcc76747824835b9acbc6d8e89159c","observedAt":"2026-11-07T12:32:23.192+00:00","statement":{"source":"euvd","id":"EUVD-2026-38549","aliases":["CVE-2026-55517","GHSA-x2qc-cmh9-f4hf"],"title":"Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.5, a Deno program that opens a client WebSocket connection could be crashed by the remote server. While handling the WebSocket handshake response, Deno parsed the Sec-W…","description":"Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.5, a Deno program that opens a client WebSocket connection could be crashed by the remote server. While handling the WebSocket handshake response, Deno parsed the Sec-WebSocket-Protocol and Sec-WebSocket-Extensions response headers in a way that assumed their bytes were always printable ASCII. A response header containing non-visible-ASCII bytes (0x80-0xFF) caused a panic that aborted the entire Deno process. This vulnerability is fixed in 2.7.5.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","score":4.3,"severity":null}],"references":["https://github.com/denoland/deno/security/advisories/GHSA-x2qc-cmh9-f4hf"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-38549","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Jun 23, 2026, 5:24:59 PM","dateUpdated":"Jun 23, 2026, 5:52:56 PM"},"relatedAdvisories":[],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-38549","identifiers":["EUVD-2026-38549","CVE-2026-55517","GHSA-x2qc-cmh9-f4hf"]},"retained":false,"historicalAffected":[]},{"revision":"4c67d86fbe624733837fbf6f73edf044","observedAt":"2026-10-27T15:15:14.036+00:00","statement":{"source":"nvd","id":"CVE-2026-55517","aliases":[],"title":"Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.5, a Deno program that opens a client WebSocket connection could be crashed by the remote server. While handling the WebSocket handshake response, Deno parsed the Sec-W…","description":"Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.5, a Deno program that opens a client WebSocket connection could be crashed by the remote server. While handling the WebSocket handshake response, Deno parsed the Sec-WebSocket-Protocol and Sec-WebSocket-Extensions response headers in a way that assumed their bytes were always printable ASCII. A response header containing non-visible-ASCII bytes (0x80-0xFF) caused a panic that aborted the entire Deno process. This vulnerability is fixed in 2.7.5.","state":0,"publishedAt":"2026-06-23T18:18:09.787+00:00","modifiedAt":"2026-10-25T23:10:00.167+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","score":4.3,"severity":"MEDIUM"}],"references":["https://github.com/denoland/deno/security/advisories/GHSA-x2qc-cmh9-f4hf"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-55517","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-248"],"productCriteria":["cpe:2.3:a:deno:deno:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-06-23T18:18:09.787","lastModified":"2026-10-25T23:10:00.167"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-55517","identifiers":["CVE-2026-55517"]},"retained":false,"historicalAffected":[]},{"revision":"628a381afd1b4ce5a4a966818dcb7b3d","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-x2qc-cmh9-f4hf","aliases":["CVE-2026-55517"],"title":"Deno: Denial of service via non-ASCII bytes in WebSocket response headers","description":"## Summary\n\nA Deno program that opens a client `WebSocket` connection could be crashed by\nthe remote server. While handling the WebSocket handshake response, Deno parsed\nthe `Sec-WebSocket-Protocol` and `Sec-WebSocket-Extensions` response headers in\na way that assumed their bytes were always printable ASCII. A response header\ncontaining non-visible-ASCII bytes (`0x80`-`0xFF`) caused a panic that aborted\nthe entire Deno process.\n\n## Details\n\nWhen establishing a client WebSocket connection, Deno read the\n`Sec-WebSocket-Protocol` and `Sec-WebSocket-Extensions` headers from the\nserver's `101 Switching Protocols` response and converted them to strings\nwithout handling the failure case. `HeaderValue::to_str()` returns an error for\nany value containing bytes outside the visible-ASCII range, so a header carrying\nsuch bytes triggered an unrecoverable error during conversion.\n\nBecause the client initiates the outbound connection, the handshake response is\nfully controlled by the server. A server that returns bytes such as `0xFF 0xFE`\nin either header could therefore crash any client that connected to it.\n\nThis is purely an availability issue. There is no information disclosure and no\nmemory-safety impact; the only effect is termination of the current process.\n\n## Impact\n\nRemote denial of service. Any Deno application that establishes WebSocket\nconnections to untrusted or potentially-compromised endpoints could be\nterminated by the remote peer. Exploitation requires the victim application to\ninitiate the outbound WebSocket connection. An attacker who controls the\nWebSocket endpoint, or who can man-in-the-middle a plaintext `ws://` connection,\ncould trigger the crash. The effect is confined to crashing the process that\nopened the connection.\n\n## Patch\n\nThe issue is fixed in Deno `2.7.5`. The header values are now parsed with\ngraceful fallbacks: values that cannot be represented as ASCII strings are\nskipped instead of aborting the process. A regression test covers a server that\nreturns non-ASCII bytes in `Sec-WebSocket-Protocol`.\n\nUsers should upgrade to Deno `2.7.5` or later.\n\n## Workarounds\n\nUntil you can upgrade, only connect to trusted WebSocket endpoints and prefer\n`wss://` (TLS) over `ws://`, which prevents a network man-in-the-middle from\ninjecting malicious header bytes into the handshake response.","state":0,"publishedAt":"2026-06-17T18:48:18+00:00","modifiedAt":"2026-06-17T19:11:27.308501+00:00","affected":[{"ecosystem":"crates.io","name":"deno","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"2.7.5"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/denoland/deno/security/advisories/GHSA-x2qc-cmh9-f4hf","https://github.com/denoland/deno"],"sourceUrl":"https://github.com/advisories/GHSA-x2qc-cmh9-f4hf","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-x2qc-cmh9-f4hf","identifiers":["GHSA-x2qc-cmh9-f4hf","CVE-2026-55517"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-cbfb00168958467aaa6015d5230faa08","complete":true,"records":13633,"lastAttemptAt":"2026-11-07T21:04:54.6100336+00:00","lastSuccessAt":"2026-11-07T21:04:54.606+00:00","error":null,"lastVerifiedAt":"2026-11-07T21:04:54.606+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13685,"expectedIdentifiers":13685,"failedIdentifiers":0},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. 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